Obsidius(オブシディアス?) (originally known as Magmouth) is a villainous entity created exclusively for the video game Godzilla: Unleashed.

Although most of the crystals deposited on Earth by the meteor showers embedded themselves in the surface, some of them managed to punch through the Earth's crust and enter the lithosphere. There, brought together by the magma flows from within the Earth, a sentient creature was brought to life by the accumulated power of the crystals and the raw, ferrous materials of the Earth. Obsidius emerged from a volcano onto the surface world only recently, and thus far has resisted all attempts at communication. Its virtually impenetrable mineral exterior shields him against both physical and energy assaults. It advances single-mindedly toward the most unstable crystal formations on the surface, and as such should be considered extremely dangerous.

Obsidius is made of volcanic rock, therefore resisting most attacks on it. It is immune to lava, and therefore can run around in the lava pool on the Seattle arena in the game. It can curl itself into a ball and roll around at a higher speed, similar to Anguirus. Many of Obsidius's attacks are similar to Orga's, with its huge arms and flexible legs playing a huge role in its attacks.

Obsidius was one of the monsters in the IGN roster that got to be game after winning in the roster. The other monsters in the roster that lost to Obsidius were Firelion, The Visitor and Lightning Bug.

Krystalak(クリスタラック?) is a villainous entity created exclusively for the game Godzilla: Unleashed. It appears in the Wii and DS versions of the game.

Krystalak is a semi-sentient crystal organism, spawned by the same meteor shower that threatens to rip the Earth apart. Born from the crystals, Krystalak seeks to bring all of their energies together to make itself into the ultimate monster. Like the crystals that spawned it, Krystalak is quite resistant to most forms of energy weapons, forcing opponents to fight him tooth and claw. With no ties to any existing alien or terrestrial powers, Krystalak seeks power at any cost.

Krystalak is born from the crystals that crashed onto Earth, therefore producing crystal based powers. It fires crystal shards as a longer range attack and can fire crystal projectiles from its tail. It has incredible agility, and can attack with great skill. Its most devastating ability is to overload its heart and cause a huge shockwave to blast around it, dealing intense damage.